The present invention relates to shutters for cameras in which a light control mechanism comprising a plurality of shutter blades, which may also function as the aperture control diaphragm, and means for intermittently opening and closing the shutter blades in response to the driving pulse signals, is controlled in response to the brightness of a subject so that the optimum exposure may be attained.
Various shutters for cameras of the type for automatically attaining the optimum exposure in response to the brightness of a subject have been devised and demonstrated. For instance, Japanese Patent Publication No. 1871/1971 has disclosed a shutter of the type in which a plurality of shutter blades, which may also function as the aperture control diaphragm, are wide opened within the order of tens of micro-seconds with the aid of a delayed action governer, and then closed after the exposure in response to the brightness of a subject has been attained. There has been also devised and demonstrated a shutter in which a desired aperture stop is set by an aperture stop control mechanism actuated by driving means with a movable coil, and then a shutter mechanism is opened for a predetermined time.
In the former type, the governor mechanism is very complex in construction, consisting of many parts which must be fabricated with severe manufacturing tolerances so that exposure characteristics tend to change when the shutter has been used for a long time.
In the latter type, the driving means with a movable coil is used so that the response to the quick change in brightness of a subject is not satisfactory. For instance, when the brightness of a subject suddenly becomes high or low immediately before the aperture stop is to be set, the aperture setting mechanism cannot respond to the change in brightness of the subject satisfactorily, resulting in an erratic exposure. Moreover, the latter type has another inherent limitation in that the driving means with a movable coil is damaged even by very weak mechanical shock. A further inherent limitation is that the mechanism is complex because both the shutter mechanism and the aperture setting mechanism must be provided. To actuate the shutter mechanism, the mechanical spring force must be charged and stored, and the spring force must be charged and stored everytime the shutter operation has been accomplished, so that the shutter cannot be opened a plurality of times in succession within a relatively very short time. When it is desired to remotely control a camera by using an electromagnetic wave control signal, a solenoid, which is energized by a battery in response to the output signal from a receiver, must be attached on the camera so that the shutter button may be depressed upon reception of the control signal. Therefore, the remotely-controlled camera equipment is very large in size.